Clutch-to-clutch (C2C) automatic transmissions generally employ current-controlled clutch pressure control solenoids to perform mainly synchronous shifts. Typically, solenoid response characteristics (e.g., pressure vs. current performance curves) for most C2C transmissions are not calibrated to a specific performance standard during manufacture. Instead, the solenoid performance characteristics are measured after solenoid manufacture with the resultant solenoid performance curves being stored in the transmission or powertrain control module during assembly integration. This data is typically not available to aftermarket manufacturers or custom vehicle builders.
An issue with creating tuning calibrations for C2C transmissions is that production variances exist in aspects of the system components such as in the response curves of the pressure control solenoids. Production variances also exist in the size and/or characteristics of other transmission components such as valve bodies, clutch assemblies, and friction materials. In typical non-customized OEM vehicles, such variances are not problematic.
However, such variances can be problematic for customized vehicles, aftermarket modified vehicles, racing vehicles, etc., where modifications are made to accommodate higher power levels and unique application requirements. Such modifications may include the use of different clutch or band friction materials with different static and dynamic friction coefficients, different numbers of friction and separator plates, different clutch pack clearances, different piston sizes, valve body modifications, and various other changes which are likely to affect transmission shift quality, and the required clutch (or band servo) pressures during a shift. Extensive changes to engine torque and power curves also significantly influence transmission operation, and would render most of the assumptions and formulas used in creating the original manufacturer's calibration data invalid, even if this data were freely available to aftermarket manufacturers. For these reasons, an OEM-style standardized tuning methodology is generally less useful for performance applications where characterization information is rarely available, and where modifications are prevalent.
Calibrating a C2C transmission from scratch without any initial characterization data is beyond the capabilities of most automotive enthusiasts. This process is so complex that an extensive training program must be completed in order to effectively and safely use some of the current aftermarket systems. The inherent synchronous nature of C2C transmission shifting also introduces a potential hazard if the transmission is improperly tuned, since these transmissions have the potential to “tie up” (by attempting to operate in two ratios at the same time), which can cause the vehicle's drive wheels to lock, leading to a potential loss of vehicle control. To this end, a system and method are needed that can easily create a safe and effective transmission calibration in the absence of factory characterization and calibration data.
Accordingly, improvements would be welcome to transmissions in general, and to C2C transmissions, systems, and methods of calibrating transmissions that address one or more drawbacks of current technology and/or any other issues.